Gravity friction switch



Aug. 27, 1929. J. B. HOFF 1,726,225

GRAVITY FRI CTION SWITCH Filed Aug. 17. 1927 2 Sheets-Sheet 1 IN'TE'NTOR@www Aug. 27, 1929. J, B -HOFF 1,726,225

GRAVITY FRICTION SWITCH Filed Aug. 17. 1927 2 Sheets-Sheet 2 PatentedAug. 27, 1929.

UNITED STATESA JOSEPH B. HOFF, F PHILADELPHIA, PENNSYLVANIA.

v(.TrIEMLVI'FY FRICTION SWITCH.

.Application led August 17, 1927. Serial No. 213,491.

My invention relates to newand useful improvements in a gravity-frictlonswltch,

and has for its primary `object to provide an exceedingly simple andeffective device of this character, whereby a mercury switch or switchesmay be actuated through the medium of a helical thermostat, theconnection between said thermostat andthe mercury switch or switches issuch as to permit actuation of the thermostat after the switch 4orswitches have been operated without further affecting the latter.

A further object of my invention is to provide means for operatingmercury switches from a thermostat without the use of the usual springs,clutches and the like.

A still further object ofthe invention is to provide a casing to bemounted at a place where changes in temperature take place, a drumprovided with a shaft or axle for rotatably mounting said drum in thecasing, a thermostat to rotate the 'drum through the medium of its shaftdue to changes 1n the temperature in the locality of the thermostat, amercury switch holder located within the drum and having itsendsmaintained by gravity in frictional engagement with the curved wall ofthe drum so as to rotate with said drum, nd yet free so as the. drum mayrotate independently of the holder, means to limit the movement of theholder intwo directions, 'and a mercury switch carried by the holder formakingand breaking electrical circuits.

With'these ends in view, this invention consists in the details ofconstruction and combination of elements hereinafter set forth and thenspecifically designated by the.`

claims. l In order that those skilled in the art to,I whichv thisinvention appertains mayunderstand how to makeand use the same, I willdescribe its construction in detail, referring by numerals to theaccompanying drawin s forming a part of this application, in whic Fig.1, is a vertical sectional view of a gravity-friction switch constructedin accordance with my invention showing its application to the smokestack of a heating desv vice, a portion of which is illustrated andparts of the apparatus left in elevation. i Fig. 2, is an outer end viewof the switch. Fig. 3, is a horizontal sectional view of the drum withthe mercury switch holder in lace.

ig. 4, is a sectionof the bearing formed TFvit-h the casing taken on theline 4 4 of ig. 5, is an edge view of the mercury switch holder per se.

Fig. 6, is an end view of Fig. 5.

Fig. 7, is a side elevation of another form of mercury switch.

Fig. 8, is a similar view showin switch tilted for completing onecircult.

In carrying out my invention as herein embodied, 10 represents a smokestack on the enclosure of another compartment or chamber, thetemperature of which is used to control the same or other temperatures.The smoke stack is merely used to illustrate an application of theinvention.

A casing 11 is suitably supported in any convenient location and itpreferably has a hub or bearing 12 provided with bracket said lugs orears 13 byl which the device may be mounted in lace as on the smokestack, in which case t e bearing projects through an opening in thestack. Within the casing is mounted a drum 14 including a rear wall 15,a curved or circular side wall 16, and a front flange 17, detachablyconnected with the drum and preferably with the side wall thereof, thusthe front of the drum is open. Projecting from the rear wall of the drumis a shaft or axle 18 which yis journalled in .the bearing or .hub 12 ofthe casing and hasV as one end projecting beyond said bearin into thesmoke stack 10. On the pro]ect ing end of the'shaft is mounted athermostat 19 preferably of helical form 'and enerally termed a helixwith 'one end xed to the shaft or axle as at 20 and the other endthrough the bearing 12 as shown at 21.

The temperature changes which take place within the smoke stack causethe thermostat 19 to expand or contract, thus imparting a rotary motionto the drum 14.

Within the drum is mounted or located a mercury switch 22 consistin oftwo tubes 23, each having two electrical conductors leading therefrom asshown in Figs, 1 and 2,

. or said switch may consist merely of a single mercury tube 24 havingtwo pairs of conductors'leading therefrom as shown in Figs. 7 and 8. lThese mercury tubes are the well known mercury switches used for makingand breaking an electrical circuit or circuits when oscillated. I

Thel mercury switch itself frictionally engages the curved side Wall 16of the drum or is provided with means to so frictionally engage the sidewall of the drum. The latter method is preferable, and for convenienceof illustration, I have shown a metal plate 25 providedswith clips 26 soarranged as to hold the tubes 23 at suitable angles opposite to eachother. The plate 25 being in frictional engagement with the side wall'ofthe drum when the latter is rotated, the plate will move with it, untilsaid plate strikes against one of the stops 27 or 28 at which timemovement of the plate 25 will be arrested, although the drum may-continue to revolve.

Where a single mercury tube is used, the plate 25 has the clips 26arranged to hold the tube 24 parallel with the plate, but the action andultimo result are the same.

The stops 27 and 28 are preferably carried by the casing 11 and are sofashioned as to project into the drum for disposition in the path oftravel ofthe ends of the plate.

Within the casing may also be mounted a panel 29 carrying binding posts30 to which are connected the ends of wires 31 leading to electricalinstruments or appliances and said wires may be in cable form as at 32if desired. Other wires 33-are connected to the binding posts 30 and tothe terminals of the mercury switch.

From the foregoing description, it will be obviousA that when atemperature change takes place within the smoke stack, which will effectthe thermostat' 19 and cause it to rotate thedrum 14 clockwise withreference to Fig. 2, the mercury switch and its plate will move withsaid drum because of the frictional engagement between the walls of saiddrum -and the plate until the oneend of said plate contacts with thestop 28, thus arresting further movement of the mercury switch, althoughone circuit is closed. After the mercury switch has stopped, should thechange in temperature be such -as to cause the thermostat to continuerotating the drum, this may occur without in any Way alfecting themercury switch. As soon as another change 'in' the temperature takesplace which causes the-thermostat to rotate the drum counter clockwise,then the switch will be moved in this direction until the opposite endof its plate contacts with the stop 27. In this condition, thepreviously closed circuit will be opened and the other electricalcircuit closed, but after this condition has'taken place, the drum maycontinueto rotate in the same direction without in any lway affectingthe mercury switch.

It is to be particularly noted that in a switch lconstructed in thismanner, the switch element or the circuit making and breaking means maycontinue to move without affecting the operation of the switch element,and this is accomplished without the use of spring, clutches or thelike, and said switch element cannot be broken or damaged, no matter howfar the operating elelment may move.

Of course'I donot wish to be limited to the exact details of`constructions as herein shown, as these may be varied within the limitsof the appended claims without departing from the spirit of myinvention.

Having thus fully described my invention, what I claim as new and usefulis:

1. A switch of the class described including a casing, a drum rotatablymounted in the casing, a plate projecting across the interior of thedrum and resting on the walls thereof, a switch element,l carried by theplate, temperature controlled means for rotating the drum, and means inthe path of travel of the ends of the plate to stop the plate after ithas moved a predetermined distance with the drum, after which said drummay continue to rotate.

2. In a device of the character stated, a

drum adapted to-be mounted for rotation, a switch plate within saiddrum, and means to hold the switch plate against movement, while lthedrum rotates.

3. A switch comprising a casing, a drum, a shaft on said drum forrotatably mounting the latter in the casing, a temperature controlledelement connected with the casing and the shaft of the drum for rotatingthe latter, a switch plate mounted within the drum and frictionallyengaging the walls thereof, a flange detachably mounted on the drum toprevent accidental displacement of the switch plate, means projectingfrom the casing into the drum in the path of travel of the ends of theswitch plate to arrest movement of the latter while permitting the drumto rotate, an electrical circuit making 4and breaking means carried bythe plate.

4. In a device of the character stated, a casing, a drum having acircular wall rotatably mounted in the casing, means controlled bytemperature changes to rotate said drum, a Switch plate within the drumand having its ends resting on the circular wall thereof, whereby it maybe rotated with the drum, and means in the path of travel of the ends ofthe plateto arrest its movement and permit rotation of the drum withoutmoving the plate.

5. A device of the kind described comprising a hollow circular rotatablemember, and a free switch element resting on the inside circular wallsof said member and movable with the latter until arrested by an outsideagency.

In testimony whereof, I have hereunto `affixed my signature.

JOSEPH B. HOFF.

